An electrical load system includes one or more electrical loads, a power transfer switch, and an electronic control system. The power transfer switch is coupled with and can provide power to one or more electrical loads from a first power source or a second power source. The electronic control system evaluates a source impedance of the first source and controls the power transfer switch in response to the source impedance of the first source indicating a fault condition of the first power source that would interrupt power from the first power source to the one or more electrical loads prior to the fault condition disrupting power from the first power source to the one or more electrical loads.